Control of Si-Based All-Dielectric Printing Color through Oxidation

All-dielectric color printing by means of high-index Mie resonators has enabled wider control of reflection colors depending on structural geometry. However, modifying the geometry, including the height, by using conventional fabrication processes remains challenging, and drastic color modification approaches via the addition of a new tuning axis are required to extend color varieties and applications. Here, we demonstrate all-dielectric pixel color control through Si oxidation. Oxidized monocrystalline Si nanostructures exhibit wider tunability of brilliant reflection colors depending on the oxidation reaction. The different color change properties of each nanostructure enable the construction of an "invisible ink" that can hide color information. This approach for controlling printing color could be utilized to further extend color variation and reactive applications.